'The Walking Dead' Recap: And This Little Piggy...

SPOILER ALERT: The recap for the "Infected" episode of "The Walking Dead" contains storyline and character spoilers.

It's probably the last little bit of calm that viewers, and certainly the survivors, are going to enjoy from "The Walking Dead" this season: Tyreese and his girlfriend, Karen, are enjoying a little couple time. As she snuggles in his lap, he tells her he can't stop thinking about Zach, the young man who died in the attack at the Big Spot store last week.

Tyreese, who's finally gotten a chance to stop and think about all the things he's had to do to survive and all the loss that has entailed, tells Karen, "Used to be, we all had acquaintances, people move in and out of your life… no big; see 'em down the road sometime. Now the handful of people you know, that's it. Might as well be the only people left in the world." And with that, he breaks out into song, crooning a bit of "I've Got You Under My Skin" for the one who clearly has gotten under his.

Sadly, the song could work on another level here, because something has gotten under, inside of, on top of, and all around the skin of the survivors, and whatever it is is making them deathly sick, then just dead, then walker-ized. When we saw sweet young newbie Patrick last, he'd just gotten through the sickness, then the death, then the turning. In "Infected," he began the official zombie portion of his story, and again, it ended what was probably the last bit of calm anyone at the prison is going to experience for quite a while.

A Zombie Breakfast: The Most Important Meal of the Day

As Rick wakes up his children and prepares to begin another day of farming, Zombie Patrick picks himself up off the bathroom floor and makes his way to another block. He almost goes into Karen's cell, but then turns into another, where he starts chomping down. When he leaves his victim, the man rolls off the bed, as his innards fall out of his open tummy.

In the guard tower, Glenn is watching Maggie sleep, and uses the camera he got at the Big Spot to snap a pic of her. He's heading down to do a perimeter check, and tells her he'll return with breakfast.

Elsewhere on this happy morning, Michonne is about to take off again on her horse, and asks Carl if there's anything special he wants her to bring back. Maybe some stale M&Ms? "You're the one who likes stale M&Ms," he jokes, and off she goes.

And then Rick and Carl start working on their cucumber patch, where Carl asks if he can help the others clear the fences. "We have other plans," Rick answers, and then Carl asks when he can have his gun back. Before Rick can answer, gunfire breaks out, Michonne races back to the prison, Rick tells Carl to go to the tower, and he runs into the prison.

"It's Like They Choked to Death on Their Own Blood"

On his way to the tower, Carl goes to open the gate for Michonne, who has drawn two walkers to herself. Carl grabs a rifle and shoots one, Maggie shoots the other with her gun, and Michonne's leg is hurt in the scuffle. Michonne was saved, but the commotion has drawn a swarm of walkers to the fences.

A walker in 'The Walking Dead' Season 4 episode, 'Infected.'

Inside the prison, the scene is even more chaotic. Walkers are inside the cell blocks, going after anything they can get their undead hands on, and several people have already been bitten. Adults and children are screaming and running, while Daryl and his bow and arrows and other more levelheaded members of the prison population are taking the walkers down.

Carol spots Ray, father of tweens Lizzie and Micah, who has been bitten on the arm. She takes him into a cell and prepares to amputate his arm to stop the bite from spreading, but it's too late: He's also been bitten on the neck. She tells Ray he needs to say goodbye to his girls, and he asks Carol to promise to take care of the girls as if they were her own. She agrees.

Rick, meanwhile, has joined the fray, unhappily, and he, Daryl, Hershel, and some of the other men notice there are no bites, no wounds on Patrick and the others who've turned. "It's like they choked to death on their own blood," says Hershel, hence the blood running down their faces. Rick says he noticed that on some of the walkers at the fence, too. They conclude it must be some sort of aggressive flu, and they more disturbingly realize that they all have now been exposed.

Meanwhile, just after Lizzie and Micah say goodbye to the father, he dies, and Carol prepares to stab him in the brain before he turns. Lizzie says she should be the one to do it, and has the knife in her hand, but can't. Carol does it.

Lizzie in a Tizzy

At a meeting of the prison council, it's decided that with this new illness present and likely to spread, they need to quarantine those who start to show signs. After all, Patrick was well one day, and by the next morning, he was eating people. So when Karen begins coughing, and she says David also has been feeling sick, it's decided the two of them will be shuffled off to a different cell block, which was also, unfortunately, death row at the prison.

Outside, as Micah and Lizzie stare at the zombies at the fence, Carol approaches and tells Lizzie she was weak in not being able to stab her father. Harsh, perhaps, but as Carol points out, being able to take actions like that is the difference between life and death. Lizzie is crying, and Carol realizes it’s not for her father… it's for Nick, the now-dead zombie with the nametag she and the other children were waving to last week. Lizzie has the worst case of Stockholm syndrome, zombie version, ever; she sympathizes more with the walkers than with her fellow humans. As Micah puts it, Lizzie isn't weak… she's messed up.

Later, Carol finds Lizzie and Micah at the fence again and tells Lizzie not to feel bad about Nick. He's a walker. She should feel bad about her dad. As Carol puts a flower in her hair, and tells her they're going to bury her dad in a place she can visit him and take flowers to him, Lizzie takes a knife from Carol and puts it on her belt.

Why Is Rick Like Carrie at the Prom?

As is so often the case for the survivors, there's never just one crisis on their plate. With the infection outbreak inside the prison, a section of the fence is about to come down outside as hoards of walkers push against it. What has been drawing them in such large numbers lately? Perhaps it's the half-eaten rats Sasha discovers on the ground? Yep, someone's been feeding them… a certain blond-haired little someone who has an unusual sympathy for them?

But back to the potential disaster at hand: The small group trying to take out walkers and hold up the collapsing fence at the same time are losing the battle when Rick tells Daryl to get the truck. "I know what to do," he says, with the Rick Grimes leadership look on his face.

Daryl's driving a jeep, with a wagon attached, and Rick's in the wagon beside a box. They go tearing off through the field outside the fence, with the walkers hot on their trail. Rick yells for Daryl to stop, and Rick picks something up out of the box.

It's a piggy, one of the piggies he and Carl have been raising. Rick cuts the pig and tosses it into the yard, where the walkers swarm on it. He has Daryl drive off further, stop, and Rick does the same thing. The look on Rick's face, which is now splattered with pig blood, says he's heartbroken about everything this means: that he had to kill the pigs, something he was tending to with his son, and most of all, that he knows it means he can't relinquish his leadership duties, and that he knows he and Carl can't live any sort of passive lifestyle in this world.

Fire Alarm

Later, Rick is dismantling the pig pen, and tells Carl they have to stay away from Judith for a while. "I don't like it, but…"

Carl then tells Rick about Carol's classes, and that she asked him not to tell Rick. Carl says he thinks Rick should allow Carol to go on teaching the kids how to kill. As has been brought home to everyone so painfully once again, it's necessary.

Rick sets the pig pen remains ablaze, and tells Carl he won't rat out Carol or try to stop her. And then he gives his son his gun back, and returns his own gun belt around his waist.

Inside the prison, Tyreese has a bouquet of flowers and is about to present them to Karen. But all he finds in her cell is a trail of blood, just like the one that Patrick left as he made his way from his sickbed to the bathroom.

Tyreese follows the trail, which leads outside. He opens the door, walks out, and a look of shock and horror crosses his face as he drops down to his knees. The camera pans to what he sees: two bodies, freshly charred, on the ground, with a gas can beside them. The bodies are burnt beyond recognition, except for one detail: One of them is wearing Karen's bracelets.

* Andrew Lincoln told us in an interview that in Episode 3, next week's "Isolation," Rick will be fully dragged back into the middle of the action at the prison. He made a valiant effort to keep himself and Carl out of violent situations, but his decision to give Carl's gun back to him, to keep quiet about Carol's weapons classes, and to strap on his own gun belt again means Rick has accepted that you just can't stick your head in the sand — or in the cucumber patch, in this instance — in a zombie apocalypse.

* Favorite quote of the night: Daryl, telling Rick he understands why he's been shying away from leadership duties, after Rick said he made "too many bad calls," and "almost lost my boy, who he was." "For what it's worth," said Daryl, when Rick came to help him bury the infected dead, "you see mistakes. I see when the s--t hits, you're standing there with a shovel."

* Favorite scene of the night: Michonne with baby Judith. "Dead" fans who've also read the comics understand why that version of Michonne might be sad around a child, so it will be interesting to find out TV Michonne's backstory, and why she sobbed as she held on tightly to Judith.

Tell us, "Deadheads": Who do you think burned the bodies? Was the gas can sitting beside their bodies the same one Rick used to burn the pig pen? Is Rick the one who set the infected duo on fire? And is this, as the "TWD" cast members have been teasing in interviews, the event that tears the survivors apart?